1. Field of the Invention
The present invention relates to a semiconductor device comprising first and second semiconductor chips which are contained in a single package and at least one of which is formed by using a wide gap semiconductor (such as silicon carbide or gallium nitride) as the base material. The following description of the present invention centers mainly on semiconductor devices for use in high voltage applications; however, the present invention is not limited to such power semiconductor devices but could be used with any kind of semiconductor devices.
2. Description of the Background Art
In applications to voltage-source inverters, in general, a switching chip having switching capability and a circulating diode chip are connected in inverse-parallel with each other.
FIG. 9 is a longitudinal cross-sectional view illustrating the configuration of a conventional module element 400 for use in voltage-source inverters. Active elements of the module element 400 each are formed by using silicon as the base material. That is, a switching chip 401 and a diode chip 402 contained in a closed container 417 are both made of silicon. The switching chip 401 has a cathode electrode 403 and a control electrode 404 formed on the front surface and an anode electrode 405 formed on the rear surface. The diode chip 402 has an anode electrode 406 formed on the front surface and a cathode electrode 407 formed on the rear surface. The anode electrode 405 of the switching chip 401 and the cathode electrode 407 of the diode chip 402 are electrically connected to each other by being soldered to a conductive plate 408 by a solder layer 409. The cathode electrode 403 and the control electrode 404 of the switching chip 401 are connected respectively to a cathode conducting bar 410 and a control conducting bar 411 by a bonding wire 413, and the anode electrode 406 of the diode 402 is connected by the bonding wire 413 to the cathode conducting bar 410. The conductive plate 408 is connected through an insulating substrate 414 to a heat sink 415 having cooling capability. Also, the conductive plate 408 is electrically connected through a metal body 416 to an anode conducting bar 412.
In this configuration, heat generated by the energy losses of the chips 401 and 402 can be dissipated from their respective rear electrodes 405 and 407 to the outside through the path formed of the solder layer 409, the conductive plate 408, the insulating substrate 414 and the heat sink 415.
However, in the configuration of the conventional module element 400 illustrated in FIG. 9, since the switching chip 401 and the diode chip 402 are both electrically and mechanically connected to the conductive plate 408, even the use of the low-loss wide gap semiconductor for production of the switching chip 401 and/or the diode chip 402 can achieve neither simplification of an element cooling mechanism nor significant reductions in the size and weight of the closed container 417 or the module element 400 itself. Accordingly, even if the chips in the module element with the configuration of FIG. 9 are replaced by wide gap semiconductor chips, reductions in the cost of the semiconductor device cannot be achieved.